Systems and methods for monitoring, inferring state of health, and optimizing efficiency of refrigeration systems

Abstract

Systems and method for operating and monitoring refrigerators are described. Temperature cycles within the compartment are characterized using statistical, frequency and pattern analysis techniques to derive a steady-state characteristic of temperature within the compartment. A thermal sensor inside the conditioned area is monitored and temperature data sets can be analyzed to determine performance in comparison to a baseline, and energy consumption. Analysis of continuous temperature readings taken from individual or groups of freezers identifies patterns of variations in temperature cycles from which feedback on efficiency can be inferred. Electrical load can be determined by measuring or estimating current usage and identifying periods of time when compressors are active in the refrigerator.

1 . A method of monitoring operational efficiency of a heating or cooling system, comprising:
 configuring a controller to collect data from one or more sensors that are configured to collect measurements from the heating or cooling system, the measurements being indicative of current usage, temperature or vibration associated with a thermodynamic cycle;   receiving, from the controller, a plurality of periodic measurements that have been collected by at least one sensor of the one or more sensors over a duration of time corresponding to multiple temperature cycles within an internal compartment in the heating or cooling system;   using the plurality of periodic measurements to generate a temperature characteristic for the heating or cooling system, the temperature characteristic being representative of performance or efficiency of the thermodynamic cycle over the multiple temperature cycles; and   identifying compressor on or off transitions based on an acceleration or a deceleration of a rate of change of temperature within a half cycle of the temperature characteristic.   
     
     
         2 . The method of  claim 1 , further comprising:
 determining a state of health of the compressor based on the temperature characteristic.   
     
     
         3 . The method of  claim 1 , wherein the heating or cooling system comprises a refrigeration system. 
     
     
         4 . The method of  claim 1 , further comprising:
 identifying differences between the temperature characteristic and a baseline characteristic that corresponds to a nominally operating system, wherein the baseline characteristic corresponds to a normalized average of temperature cycles obtained from a population of heating or cooling systems.   
     
     
         5 . The method of  claim 4 , wherein the population of heating or cooling systems comprises different types of heating or cooling systems. 
     
     
         6 . The method of  claim 1 , wherein the plurality of periodic measurements includes measurements of temperature or electrical current that are sampled at a frequency calculated to capture a fundamental frequency of temperature change. 
     
     
         7 . The method of  claim 1 , wherein the period of each of the multiple temperature cycles corresponds to a period of the thermodynamic cycle. 
     
     
         8 . The method of  claim 1 , further comprising:
 determining that a pump is engaged based on presence of one or more harmonic frequencies in the temperature characteristic.   
     
     
         9 . The method of  claim 1 , further comprising:
 determining state of a refrigerant based on the temperature characteristic.   
     
     
         10 . A non-transitory computer-readable medium having instructions stored thereon, wherein the instructions, when executed by a processor, cause the processor to:
 configure a controller to collect data from one or more sensors that are configured to collect measurements from a heating or cooling system, the measurements being indicative of current usage, temperature or vibration associated with a thermodynamic cycle;   receive, from the controller, a plurality of periodic measurements that have been collected by at least one sensor of the one or more sensors over a duration of time corresponding to multiple temperature cycles within an internal compartment in the heating or cooling system;   use the plurality of periodic measurements to generate a temperature characteristic for the heating or cooling system, the temperature characteristic being representative of performance or efficiency of the thermodynamic cycle over the multiple temperature cycles; and   identify compressor on or off transitions based on an acceleration or a deceleration of a rate of change of temperature within a half cycle of the temperature characteristic.   
     
     
         11 . The computer-readable medium of  claim 10 , wherein the instructions further cause the processor to:
 determine a state of health of the compressor based on the temperature characteristic.   
     
     
         12 . The computer-readable medium of  claim 10 , wherein the heating or cooling system comprises a refrigeration system. 
     
     
         13 . The computer-readable medium of  claim 10 , wherein the instructions further cause the processor to:
 identify differences between the temperature characteristic and a baseline characteristic that corresponds to a nominally operating system, wherein the baseline characteristic corresponds to a normalized average of temperature cycles obtained from a population of heating or cooling systems.   
     
     
         14 . The computer-readable medium of  claim 13 , wherein the population of heating or cooling systems comprises different types of heating or cooling systems. 
     
     
         15 . The computer-readable medium of  claim 10 , wherein the plurality of periodic measurements includes measurements of temperature or electrical current that are sampled at a frequency calculated to capture a fundamental frequency of temperature change. 
     
     
         16 . The computer-readable medium of  claim 10 , wherein the period of each of the multiple temperature cycles corresponds to a period of the thermodynamic cycle. 
     
     
         17 . The computer-readable medium of  claim 10 , wherein the instructions further cause the processor to:
 determine that a pump is engaged based on presence of one or more harmonic frequencies in the temperature characteristic.   
     
     
         18 . The computer-readable medium of  claim 10 , wherein the instructions further cause the processor to:
 determine state of a refrigerant based on the temperature characteristic.   
     
     
         19 . A non-transitory computer-readable medium having instructions stored thereon, wherein the instructions, when executed by a processor, cause the processor to:
 configure a controller to collect data from one or more sensors that are configured to collect measurements from a heating or cooling system, the measurements being indicative of current usage, temperature or vibration associated with a thermodynamic cycle;   receive, from the controller, a plurality of periodic measurements that have been collected by at least one sensor of the one or more sensors over a duration of time corresponding to multiple temperature cycles within an internal compartment in the heating or cooling system;   use the plurality of periodic measurements to generate a temperature characteristic for the heating or cooling system, the temperature characteristic being representative of performance or efficiency of the thermodynamic cycle over the multiple temperature cycles, wherein the temperature characteristic is expressed as a statistical moving average based on the multiple temperature cycles of the internal compartment;   identify differences between the temperature characteristic and a baseline characteristic that corresponds to performance or efficiency of a nominally operating system; and   determine an inefficiency or dysfunction of the thermodynamic cycle based on the differences.   
     
     
         20 . The computer-readable medium of  claim 19 , wherein the instructions further cause the processor to:
 predict failure of the heating or cooling system based on the inefficiency or dysfunction of the thermodynamic cycle.   
     
     
         21 . The computer-readable medium of  claim 19 , wherein the baseline characteristic corresponds to a normalized average of temperature cycles obtained from a population of heating or cooling systems, wherein the population of heating or cooling systems comprises different types of heating or cooling systems.